Brief communication:
Swimming and diving behavior in apes (Pan troglodytes and Pongo pygmaeus):
first documented report
Renato Bender & Nicole Bender 2013
Am.J.phys.Anthrop.152:156–162
doi org/10.1002/ajpa.22338

Extant hominoids incl. humans are well known for their inability to swim instinctively.
We report swimming & diving in 2 captive apes, using visual observation & video recording.
1 common chimp & 1 orangutan swam repeatedly at the water-surface over a distance of 2–6 m, both individuals submerged repeatedly.
We show:
apes are able to overcome their negative buoyancy by deliberate swimming, using movements which deviate from the doggy-paddle pattern observed in other primates.
We suggest:
apes' poor swimming ability is due to behavioral, anatomical & neuro-motor changes, related to an adaptation to arboreal life in their early phylogeny..
This strong adaptive focus on arboreal life led to decreased opportunities to interact with water-bodies, and consequently to a reduction of selective pressure to maintain innate swimming behavior.
As the doggy paddle is ass.x quadrupedal walking, a deviation from terrestrial locomotion might have interfered with the fixed rhythmic action patterns responsible for innate swimming.

Chimpanzees, Orangutans Can Swim and Dive, Biologists Prove
NS 16.8.13 Natali Anderson

2 biologists (Am.J.phys.Anthrop.) say that they have documented for the first time the swimming & diving behavior in apes.
Cooper the chimp was raised by humans, and had learned to swim.

For many years, zoos have used water moats to confine chimps, gorillas or orangutans. When apes ventured into deep water, they often(!! --mv) drowned.
Some argued that this indicated a definitive difference between humans & apes: people enjoy the water, and are able to learn to swim, while apes prefer to stay on dry land.

Renato Bender (univ.Witwatersrand Jo'sburg) & Nicole Bender (univ.Bern) have studied a chimp & an orang in the US:
Cooper the chimp & Suryia the orang were raised & cared for by humans, and have learned to swim & to dive:
“We were extremely surprised when the chimp Cooper dived repeatedly into a swimming pool in Missouri, and seemed to feel very comfortable.”
To prevent Cooper from drowning, the biologists stretched 2 ropes over the deepest part of the pool.
Cooper became immediately interested in the ropes, and after a few minutes, he started diving into the 2-m-deep water to pick up objects on the bottom of the pool:
“It was very surprising behavior for an animal that is thought to be very afraid of water.”
Some weeks later, the chimp began to swim on the surface of the water.

Suryia was filmed in a private zoo in S.Carolina. She also possesses this rare swimming & diving ability. Suryia can swim freely up to 12 m.
Both animals use a leg movement similar to the human breaststroke ‘frog kick’.
Cooper moves the hind legs synchronous, Suryia moves them alternatively.
The team believes:
this swimming-style might be due to an ancient adaptation to an arboreal life.
Most mammals use the so-called dog-paddle, a mode of locomotion that they employ instinctively, humans & apes must learn to swim.
The tree-dwelling ancestors of apes had less opportunity to move on the ground:
they developed alternative strategies to cross small rivers, wading in an upright position, or using natural bridges. They lost the instinct to swim.
Humans also do not swim instinctively. But unlike apes, humans are attracted to water, and can learn to swim & to dive.
Nicole Bender:
“The behavior of the great apes in water has been largely neglected in anthropology.
That’s one of the reasons why swimming in apes was never before scientifically described, although these animals have otherwise been studied very thoroughly.
We did find other well-documented cases of swimming & diving apes, but Cooper & Suryia are the only ones we were able to film.
We still do not know when the ancestors of humans began to swim & dive regularly.”
Renato Bender: “This issue is becoming more & more the focus of research. There is still much to explore.”

(aquarboreal wading in Hominoidea is at least early-Miocene IMO,
regular diving in archaic Homo is possibly only early-Pleistocene?? --mv)

> Brief communication:
> Swimming and diving behavior in apes (Pan troglodytes and Pongo pygmaeus):
> first documented report
> Renato Bender & Nicole Bender 2013
> Am.J.phys.Anthrop.152:156–162
> doi org/10.1002/ajpa.22338
>
> Extant hominoids incl. humans are well known for their inability to swim instinctively.
> We report swimming & diving in 2 captive apes, using visual observation & video recording.
> 1 common chimp & 1 orangutan swam repeatedly at the water-surface over a distance of 2–6 m, both individuals submerged repeatedly.
> We show:
> apes are able to overcome their negative buoyancy by deliberate swimming, using movements which deviate from the doggy-paddle pattern observed in other primates.
> We suggest:
> apes' poor swimming ability is due to behavioral, anatomical & neuro-motor changes, related to an adaptation to arboreal life in their early phylogeny.
> This strong adaptive focus on arboreal life led to decreased opportunities to interact with water-bodies, and consequently to a reduction of selective pressure to maintain innate swimming behavior.
> As the doggy paddle is ass.x quadrupedal walking, a deviation from terrestrial locomotion might have interfered with the fixed rhythmic action patterns responsible for innate swimming.